Force feel actuator fault detection with directional threshold

• US 4,294,162 A
• Filed: 07/23/1979
• Issued: 10/13/1981
• Est. Priority Date: 07/23/1979
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Fowler, Donald W., Clelford, Douglas H.
• Primary Examiner(s): Maslousky, Paul E.
• Application Number:
  US06/060,093
• Time in Patent Office: 813 Days
• Field of Search: 91/434, 91/437, 91/361, 91/363 R, 91/363 A, 91/370, 91/390, 244/83 D, 244/178, 244/196, 244/197
• US Class Current: 91/434
• CPC Class Codes: G05D 1/0055 with safety arrangements
• CPC Class Codes: G05D 1/0061 for transition from automatic pilot to manual pilot and vice versa

Abstract

In a system which provides feel-force to the control stick of an aircraft by means of hydraulic pressure, a fault indicating system which responds to excessive differences between desired and actual force in the actuator, only of a polarity in the same direction as concurrent stick motion, to separate pilot induced pressure excesses from force-system faults, is provided with directional sensitivity in the fault-indicating output logic. Excessive pressure errors in either direction of stick travel institute the monitoring of changes in stick position. Changes in stick position of an excessive magnitude are recognized as fault only if they occur in the same direction as the direction of excessive pressure error. A simple analog embodiment utilizes threshold detectors and a track store device; a dedicated-digital embodiment utilizes comparators, registers and a subtractor; and a computer embodiment utilizes a software routine.

Claims

1. An improved fault detector for a force feel system having an hydraulic actuator responsive to the difference in pressure of hydraulic fluid applied to opposite ends thereof through a turn-on valve to apply force in either of two directions to the control stick of an aircraft, the fault detector including:

means for providing a desired force signal indicative of the force desired to be applied to the control stick by the actuator;

means for providing an actual force signal indicative of the force applied by the actuator to the control stick;

error means responsive to said desired force signal and said actual force signal for providing force error signals indicative of the magnitude and direction of the difference between the desired force and the actual force applied by said actuator;

position means for providing control stick position signals indicative of the position of said control stick; and

signal processing means connected to said position means and said error means, and responsive to the amount and direction of control stick motion, which occurs directly subsequent to said error means generating a signal indicative of an excessive force in either of said directions, for providing a fault signal to close said turn-on valve in response to excessive stick motion in the same direction as the direction of excessive force;

in which the improvement in said signal processing means comprises means continually responsive to current ones of said control stick position signals for registering the control stick position indicated by said signals in response to said error means providing signals indicative of excessive force in either direction, to provide base position signals, for comparing said control stick position signals with said base position signals, for providing a first signal in response to said base position signals exceeding said current position signals by a threshold magnitude, for providing a second signal in response to said current position signals exceeding said base position signals by a threshold magnitude, and for generating said fault signal in response to said error means providing signals indicative of excessive force in a first direction concurrently with said first signal or in response to said error means providing signals indicative of excessive force in a second direction concurrently with said second signal.

2. The improvement according to claim 1 wherein said signal processing means includes:

a pair of first threshold detectors responsive to said force error signals for providing signals indicative of excessive force in corresponding directions;

a summing junction responsive to said control stick position signals;

a track store circuit responsive to said control stick position signals and to said first threshold detectors for storing said control stick position signals in response to excessive force in either direction, the output of said track store circuit being applied to said summing junction;

a pair of second threshold detectors responsive to the output of said summing junction; and

means responsive to said first threshold detectors and to said second threshold detectors to provide said fault signal only upon concurrence of output from one threshold detector in each pair corresponding to the same direction.

3. The improvement according to claim 1 wherein said signal processing means includes:

a plurality of reference registers;

a pair of first comparators, each responsive to said force error signals and a related one of said reference registers for providing signals indicative of excessive force in a corresponding direction;

a current register responsive to said control stick position signals for providing signals indicative of current stick positions;

a base register responsive to said control stick position signals and to said first comparators for storing said control stick position signals in response to excessive force in either direction;

a subtractor responsive to said current register and to said base register for providing signals indicative of the magnitude and direction of the difference in stick positions represented thereby;

a second comparator responsive to the output of said subtractor and a related one of said reference registers; and

means responsive to said first comparators and to said second comparator to provide said fault signal only upon concurrence of output from said second comparator and the one of said first comparators corresponding in direction to the direction indicated by the signals provided by said subtractor.

4. The improvement according to claim 1 wherein said signal processing means comprises a digital computer programmed to compare said force error signals with threshold magnitudes of two different directions, to update a base position register whenever the threshold magnitudes of pressure error are not exceeded, to compare the difference between a current stick position and a position indicated by said base position register against a related position threshold of either of two different directions in the event that one of said pressure thresholds corresponding to the same direction is exceeded, and to provide said fault signal in the event that either one of said position thresholds is exceeded.